1. Field of the Invention
This invention relates to electromagnetic wave absorbers and more particularly to multi-layer type electromagnetic wave absorbers which comprise a surface layer made of a composite of fibers having high electrical specific resistance and a resin as well as a wave absorbing layer made of a composite containing silicon carbide fibers having low electrical specific resistance whereby the absorbers can be lightweight and excellent in attenuation ability, broad-band wave absorbability and weatherproofness and they can also be excellent in physical properties such as mechanical strength.
2. Prior Art
It has heretofore been well known that multi-layer type wave absorbers prepared by laminating various composites have broad-band wave absorbability. In conventional multi-layer type wave absorbers, the materials composing the surface layer are different from those composite of glass fibers or Kevlar fibers and a resin incorporated with ferrite or carbon powder as material for the wave absorbing layer.
However, a conventional wave absorbing layer made of the above materials is disadvantageous in that it causes the resulting wave absorber to have low strength as a whole due to its low strength. In addition, a conventional wave absorbing layer made of the ferrite-containing resin is disadvantageous in that it causes the resulting wave absorber to be heavy in weight due to the high specific gravity of said resin. Further, when a wave absorber is constructed from surface and wave absorbing layers whose respective materials are different from each other, it will be not only low in strength but also early degradable as a structure due to the differences in thermal expansion, mechanical properties and the like between the surface and wave absorbing layers.